The Toyama No. 5 apartment block is quiet at midday -- laundry flapping from balconies, old people taking an after-lunch stroll. But the building and its nearby park may be sitting on a gruesome World War II secret.

A wartime nurse has broken more than 60 years of silence to reveal her part in burying dozens, perhaps hundreds, of bodies there as American forces occupied the capital.

The way experts see it, these were no ordinary casualties of war, but possible victims of Japan's shadowy wartime experiments on live prisoners of war -- an atrocity that has never been officially recognized by the government but is well documented by historians and participants.